focalist

I think you may be completely missing the point of Arduino.... Doing it yourself is the fun.

You haven't described what you want (LED christmas tree... you mean something life sized, a toy, is this a desktop thing or a yard decoration, what do you want the LED's to be doing, etc etc) with enough clarity to even begin to suggest a possible solution. We are pretty good around here, but we aren't good enough to read minds

If this is a gift, then maybe a Velleman kit is a better choice...If this is a school project, then do your own homework...If this is a commercial project, then do your own R&D....

It seems that you haven't thought this through, are you expecting us to do all of the thinking? At least give us an idea of WHAT you want and WHY it needs to be a completed, packaged, ready to go "kit".... otherwise this really sounds like a kid who wants a shortcut for a class project..